WORLDVIEW: The Arab-Israeli conflict has reached a turning point. With the Palestinians now tearing each other apart and Lebanon teetering on the brink of another civil war, the international community will be obliged to act. But direct military intervention will come at a price, writes Dr Rosemary Hollis.
The dividing lines are not clear cut. The multinational forces deployed in Lebanon under the Unifil banner may be able to hold the peace on the Israel-Lebanese border, but cannot stop the bombings, assassinations and fighting around the Palestinian refugee camps that threaten to destabilise the country.
In Gaza and the West Bank the violence is internecine. To side with the Palestinian president and his Fatah forces would be to take on the Islamist movement Hamas that won Palestinian elections in January last year, and become embroiled. To impose order on both sides would be to shoulder the burden of the future of Palestine, which cannot be resolved without Israeli co-operation.
Yet this was a dilemma in the making since the members of the Quartet - the UN, EU, US and Russia - decided to boycott the Hamas-led Palestinian Authority last year. By not foreseeing the likely consequences, now manifest, all the parties in the Quartet are faced with the task of picking up the mess they helped create.
Hamas militants are claiming victory over their secularist Fatah rivals in the crowded streets and refugee camps of the Gaza Strip. But Fatah, the party of Palestinian president Mahmoud Abbas, will not bow to the same fate in the West Bank.
As the fighting spreads, the possibility of the Palestinians achieving statehood by agreement, ending 40 years of Israeli occupation, recedes. Palestinian in-fighting will destroy what is left of the Palestinian Authority set up to manage Palestinian civil administration and internal security under the Oslo peace process in the 1990s.
In Lebanon, last Wednesday's assassination of an anti-Syrian politician was only the latest in a series of killings which threaten to fragment Lebanon's fragile national unity. Many Lebanese see the hand of Syria behind this and other violent incidents, notably the killing of former prime minister Rafik al-Hariri in 2005 and the recent clashes with the Lebanese army instigated by an al-Qaeda cell operating out of Palestinian refugee camps in Lebanon.
Hizbullah, long supported by Syria (and Iran) wants the resignation of the Lebanese government of Fouad Siniora, which would scupper the independent inquiry into the death of al-Hariri.
Hamas fighters in Gaza take their inspiration from Hizbullah. Their leader, Khaled Mishal, issues instructions from the Syrian capital, Damascus.
Thus it is that the spectre of civil war threatens both Lebanon and the Palestinians, with the refugee camps to the forefront. The cramped and densely populated Gaza Strip is effectively one big refugee camp, hemmed in behind the fences that delineate the border with Israel. Latterly, the construction of Israel's security barrier in and around the West Bank, together with hundreds of military check points and ever-expanding Israeli settlements, have corralled Palestinians there into disconnected enclaves.
In these circumstances, it is impossible to discern where exactly an international peacekeeping force could be inserted. Israeli forces already man the borders between the Palestinian enclaves and control the perimeter of the Gaza Strip. If a UN force takes over, they would effectively become the new masters of the fate of the Palestinians.
That said, Palestinians have long called for international intervention. Even some Israelis now want to entertain the idea. Once inserted, the problem for such forces, however, would be the end game. Are they to instigate a new "trusteeship" pending Palestinian independence? And in the meantime, with which of the Palestinian factions should they make common cause?
In January last year the EU financed and monitored the Palestinian elections that Hamas won. But then the EU joined the other members of the Quartet in boycotting the Hamas-led Palestinian Authority unless and until Hamas renounced violence, recognised Israel and accepted all previous agreements entered into by the Palestinian leadership - previously dominated by Fatah.
In his leaked "End of Mission" report, UN official Alvaro de Soto claims that the US pressured the Quartet to boycott Hamas in the hope of driving the movement from power. Washington has also provided assistance to security forces grouped around Mahmoud Abbas and now fighting Hamas.
Washington is also shipping arms to the Lebanese army, to bolster the Siniora government.
In other words, Washington has taken sides and, by going along with the boycott of Hamas, the other members of the Quartet are partially complicit.
To be considered neutral, a UN and/or EU interventionary force in Palestine would have to distinguish itself from the US agenda or else buy into it. Israeli approval would be needed in any case, to make deployment feasible. Either way, the interveners could end up being hostages in a regional and local confrontation.
That is the danger which already haunts Unifil in south Lebanon.
So what are the options? Either the Palestinians will be left to fight it out, no doubt with the Egyptians and other Arabs trying as best they can to mediate between the warring parties. But that does not promise a long-term fix. Or else the EU and UN will have to enter the fray directly, with Washington breathing down their necks, and mastermind a resolution.
The only end game in both cases, and the one long endorsed by most of the players, is a two-state solution, including a formula for resolving the Palestinian refugee issue. Whether this can be managed by international intervention in the face of so much violence and disagreement is doubtful, but the time for sitting on the fence has run out.
Dr Rosemary Hollis is director of research at the Royal Institute of International Affairs in London, also known as Chatham House. Her area of expertise is foreign policy and security issues in the Middle East, especially European, UK and US relations with the region and transatlantic differences over the issues.